Snow Is Down and Heat Is Up in the Arctic, Report Says

SAN FRANCISCO — The Arctic continues to warm faster than the rest of the globe, and with greater repercussions, scientists are reporting.

The new findings appear in the Arctic Report Card, first published in 2006 by the National Oceanic and Atmospheric Administration and updated annually. The report card catalogs the wide-ranging changes caused by the rising temperatures, in large part driven by emissions of greenhouse gases.

Snow cover, measured since 1967, was below average and set a record low in April in the Eurasian region of the Arctic. Sea surface temperatures are rising, particularly in the Chukchi Sea, northwest of Alaska, where the waters are warming at a rate of almost one degree Fahrenheit per decade.

The extent of Arctic sea ice, which retreats in summer, did not hit a record low in 2014. But it was the sixth lowest since satellite measurements began in 1979, and the scientists noted that the eight smallest extents have occurred in the last eight years.

“We can’t expect records every year,” Martin Jeffries of the Office of Naval Research, who edited this year’s report, said at a news conference here at the fall meeting of the American Geophysical Union. “It need not be spectacular for the Arctic to continue to be changing.”

With less sea ice and more open water, sunlight entered more of the ocean, leading to a bloom of tiny marine plants. On land, the greenness of the tundra continues to increase, the report said, indicating fewer snow-covered areas.

The decline in sea ice also diminished the number of polar bears in western Hudson Bay in Canada from 1987 to 2011, but populations appeared to be stable elsewhere. Polar bears rely on sea ice to travel and hunt.

In Greenland, scientists observed that melting occurred on almost 40 percent of the ice sheet during the summer, and in August, the ice sheet reflected less of the sunlight than at any time since the beginning of satellite observations in 2000. In a separate news conference, scientists reported that NASA satellite measurements have confirmed that a darker, less reflective Arctic absorbs more heat and accelerates melting.

The mass of the Greenland ice sheet, however, remained steady from 2013 to 2014, compared with major losses two years ago. The report card also noted the unusual jet-stream wind pattern last winter, often labeled the polar vortex, that led to frigid weather across much of the United States but balmy temperatures in Alaska.

The NASA reflectivity measurements found that since 2000, the amount of absorbed solar radiation in the Arctic during the summer months rose 5 percent. No significant change was seen for the rest of the planet. The Arctic areas with the greatest increases corresponded to the areas of declining sea ice. The change is equivalent to a 10-watt light bulb shining over every square meter, or 10.76 square feet, of the Arctic Ocean. In areas of greater warming, like the Beaufort Sea north of Alaska, the increase is 50 watts per square meter.

Many scientists expect the Arctic to become ice-free in summer by the end of the century, with some predicting that it could happen much sooner.

“I think the important point about the models is not to dwell on the fact that they differ, but it is to dwell on the similarities,” Dr. Jeffries said. “They all point in the same direction.” The decline of ice will continue to affect life in the Arctic. It will also open up shipping lanes and the possibility of oil drilling. “You don’t have to go to zero for these to become a big deal,” Dr. Jeffries said.

Year-to-year variability also remains large, so much so that it is not certain that the extent of sea ice will shrink in the near future.

“If someone asked me if sea ice is going to go up or down in a decade, I’d flip a coin,” said Jennifer Kay, an atmospheric scientist at the University of Colorado. But she also had no doubts about the long-term trend toward a warmer Arctic with less ice.

“If it’s 30 or 40 years out,” she said, “I have no need to flip a coin.”

A version of this article appears in print on , on Page A6 of the New York edition with the headline: Snow Down and Heat Up in the Arctic, Report Says. Order Reprints | Today’s Paper | Subscribe